Track doc building dependencies

A requirements list for the Python packages used to build project
documentation.

diff --git a/doc/requirements.txt b/doc/requirements.txt
new file mode 100644 (file)
index 0000000..ca1e4d4
--- /dev/null
+++ b/doc/requirements.txt
@@ -0,0 +1,5 @@
+# Copyright (c) 2018 Jeremy Stanley <fungi@yuggoth.org>. Permission
+# to use, copy, modify, and distribute this software is granted under
+# terms provided in the LICENSE file distributed with this software.
+
+sphinx